Mapping RNA-protein interactions with subcellular resolution using colocalization CLIP.

RNA-binding proteins (RBPs) are essential for RNA metabolism and profoundly impact health and disease. The subcellular organization of RBP interaction networks with target RNAs remains largely unexplored. Here, we develop colocalization CLIP (coCLIP), a method that combines cross-linking and immunoprecipitation (CLIP) with proximity labeling, to explore in-depth the subcellular RNA interactions of the RBP human antigen R (HuR). Using this method, we uncover HuR's dynamic and location-specific interactions with RNA, revealing alterations in sequence preferences and interactions in the nucleus, cytosol, or stress granule (SG) compartments. We uncover HuR's unique binding preferences within SGs during arsenite stress, illuminating intricate interactions that conventional methodologies cannot capture. Overall, coCLIP provides a powerful method for revealing RBP-RNA interactions based on localization and lays the foundation for an advanced understanding of RBP models that incorporate subcellular location as a critical determinant of their functions.

Hepatitis B virus RNAs co-opt ELAVL1 for stabilization and CRM1-dependent nuclear export.

Hepatitis B virus (HBV) chronically infects 296 million people worldwide, posing a major global health threat. Export of HBV RNAs from the nucleus to the cytoplasm is indispensable for viral protein translation and genome replication, however the mechanisms regulating this critical process remain largely elusive. Here, we identify a key host factor embryonic lethal, abnormal vision, Drosophila-like 1 (ELAVL1) that binds HBV RNAs and controls their nuclear export. Using an unbiased quantitative proteomics screen, we demonstrate direct binding of ELAVL1 to the HBV pregenomic RNA (pgRNA). ELAVL1 knockdown inhibits HBV RNAs posttranscriptional regulation and suppresses viral replication. Further mechanistic studies reveal ELAVL1 recruits the nuclear export receptor CRM1 through ANP32A and ANP32B to transport HBV RNAs to the cytoplasm via specific AU-rich elements, which can be targeted by a compound CMLD-2. Moreover, ELAVL1 protects HBV RNAs from DIS3+RRP6+ RNA exosome mediated nuclear RNA degradation. Notably, we find HBV core protein is dispensable for HBV RNA-CRM1 interaction and nuclear export. Our results unveil ELAVL1 as a crucial host factor that regulates HBV RNAs stability and trafficking. By orchestrating viral RNA nuclear export, ELAVL1 is indispensable for the HBV life cycle. Our study highlights a virus-host interaction that may be exploited as a new therapeutic target against chronic hepatitis B.

Phosphorylation at the disordered N-end makes HuR accumulate and dimerize in the cytoplasm.

Human antigen R (HuR) is an RNA binding protein mainly involved in maintaining the stability and controlling the translation of mRNAs, critical for immune response, cell survival, proliferation and apoptosis. Although HuR is a nuclear protein, its mRNA translational-related function occurs at the cytoplasm, where the oligomeric form of HuR is more abundant. However, the regulation of nucleo-cytoplasmic transport of HuR and its connection with protein oligomerization remain unclear. In this work, we describe the phosphorylation of Tyr5 as a new hallmark for HuR activation. Our biophysical, structural and computational assays using phosphorylated and phosphomimetic HuR proteins demonstrate that phosphorylation of Tyr5 at the disordered N-end stretch induces global changes on HuR dynamics and conformation, modifying the solvent accessible surface of the HuR nucleo-cytoplasmic shuttling (HNS) sequence and releasing regions implicated in HuR dimerization. These findings explain the preferential cytoplasmic accumulation of phosphorylated HuR in HeLa cells, aiding to comprehend the mechanisms underlying HuR nucleus-cytoplasm shuttling and its later dimerization, both of which are relevant in HuR-related pathogenesis.

Tankyrase-1 regulates RBP-mediated mRNA turnover to promote muscle fiber formation.

Poly(ADP-ribosylation) (PARylation) is a post-translational modification mediated by a subset of ADP-ribosyl transferases (ARTs). Although PARylation-inhibition based therapies are considered as an avenue to combat debilitating diseases such as cancer and myopathies, the role of this modification in physiological processes such as cell differentiation remains unclear. Here, we show that Tankyrase1 (TNKS1), a PARylating ART, plays a major role in myogenesis, a vital process known to drive muscle fiber formation and regeneration. Although all bona fide PARPs are expressed in muscle cells, experiments using siRNA-mediated knockdown or pharmacological inhibition show that TNKS1 is the enzyme responsible of catalyzing PARylation during myogenesis. Via this activity, TNKS1 controls the turnover of mRNAs encoding myogenic regulatory factors such as nucleophosmin (NPM) and myogenin. TNKS1 mediates these effects by targeting RNA-binding proteins such as Human Antigen R (HuR). HuR harbors a conserved TNKS-binding motif (TBM), the mutation of which not only prevents the association of HuR with TNKS1 and its PARylation, but also precludes HuR from regulating the turnover of NPM and myogenin mRNAs as well as from promoting myogenesis. Therefore, our data uncover a new role for TNKS1 as a key modulator of RBP-mediated post-transcriptional events required for vital processes such as myogenesis.

HuR-miRNA complex activates RAS GTPase RalA to facilitate endosome targeting and extracellular export of miRNAs.

Extracellular vesicles-mediated exchange of miRNA cargos between diverse types of mammalian cells is a major mechanism of controlling cellular miRNA levels and activity, thus regulating the expression of miRNA-target genes in both donor and recipient cells. Despite tremendous excitement related to extracellular vesicles-associated miRNAs as biomarkers or having therapeutic potential, the mechanism of selective packaging of miRNAs into endosomes and multivesicular bodies for subsequent extracellular export is poorly studied due to the lack of an in vitro assay system. Here, we have developed an in vitro assay with endosomes isolated from mammalian macrophage cells to follow miRNA packaging into endocytic organelles. The synthetic miRNAs, used in the assay, get imported inside the isolated endosomes during the in vitro reaction and become protected from RNase in a time- and concentration-dependent manner. The selective miRNA accumulation inside endosomes requires both ATP and GTP hydrolysis and the miRNA-binding protein HuR. The HuR-miRNA complex binds and stimulates the endosomal RalA GTPase to facilitate the import of miRNAs into endosomes and their subsequent export as part of the extracellular vesicles. The endosomal targeting of miRNAs is also very much dependent on the endosome maturation process that is controlled by Rab5 protein and ATP. In summary, we provide an in vitro method to aid in the investigation of the mechanism of miRNA packaging process for its export from mammalian macrophage cells.

Human antigen R transfers miRNA to Syntaxin 5 to synergize miRNA export from activated macrophages.

Intercellular miRNA exchange acts as a key mechanism to control gene expression post-transcriptionally in mammalian cells. Regulated export of repressive miRNAs allows the expression of inflammatory cytokines in activated macrophages. Intracellular trafficking of miRNAs from the endoplasmic reticulum to endosomes is a rate-determining step in the miRNA export process and plays an important role in controlling cellular miRNA levels and inflammatory processes in macrophages. We have identified the SNARE protein Syntaxin 5 (STX5) to show a synchronized expression pattern with miRNA activity loss in activated mammalian macrophage cells. STX5 is both necessary and sufficient for macrophage activation and clearance of the intracellular pathogen Leishmania donovani from infected macrophages. Exploring the mechanism of how STX5 acts as an immunostimulant, we have identified the de novo RNA-binding property of this SNARE protein that binds specific miRNAs and facilitates their accumulation in endosomes in a cooperative manner with human ELAVL1 protein, Human antigen R. This activity ensures the export of miRNAs and allows the expression of miRNA-repressed cytokines. Conversely, in its dual role in miRNA export, this SNARE protein prevents lysosomal targeting of endosomes by enhancing the fusion of miRNA-loaded endosomes with the plasma membrane to ensure accelerated release of extracellular vesicles and associated miRNAs.

Increased expression of long non-coding RNA FIRRE promotes hepatocellular carcinoma by HuR-CyclinD1 axis signaling.

There is a critical need to understand the disease processes and identify improved therapeutic strategies for hepatocellular carcinoma (HCC). The long noncoding RNAs (lncRNAs) display diverse effects on biological regulations. The aim of this study was to identify a lncRNA as a potential biomarker of HCC and investigate the mechanisms by which the lncRNA promotes HCC progression using human cell lines and in vivo. Using RNA-Seq analysis, we found that lncRNA FIRRE was significantly upregulated in hepatitis C virus (HCV) associated liver tissue and identified that lncRNA FIRRE is significantly upregulated in HCV-associated HCC compared to adjacent non-tumor liver tissue. Further, we observed that FIRRE is significantly upregulated in HCC specimens with other etiologies, suggesting this lncRNA has the potential to serve as an additional biomarker for HCC. Overexpression of FIRRE in hepatocytes induced cell proliferation, colony formation, and xenograft tumor formation as compared to vector-transfected control cells. Using RNA pull-down proteomics, we identified HuR as an interacting partner of FIRRE. We further showed that the FIRRE-HuR axis regulates cyclin D1 expression. Our mechanistic investigation uncovered that FIRRE is associated with an RNA-binding protein HuR for enhancing hepatocyte growth. Together, these findings provide molecular insights into the role of FIRRE in HCC progression.

Poly (ADP-ribose) polymerase 1 promotes HuR/ELAVL1 cytoplasmic localization and inflammatory gene expression by regulating p38 MAPK activity.

Post-transcriptional regulation of cytokine/chemokine mRNA turnover is critical for immune processes and contributes to the mammalian cellular response to diverse inflammatory stimuli. The ubiquitous RNA-binding protein human antigen R (HuR) is an integral regulator of inflammation-associated mRNA fate. HuR function is regulated by various post-translational modifications that alter its subcellular localization and ability to stabilize target mRNAs. Both poly (ADP-ribose) polymerase 1 (PARP1) and p38 mitogen-activated protein kinases (MAPKs) have been reported to regulate the biological function of HuR, but their specific regulatory and crosstalk mechanisms remain unclear. In this study, we show that PARP1 acts via p38 to synergistically promote cytoplasmic accumulation of HuR and stabilization of inflammation-associated mRNAs in cells under inflammatory conditions. Specifically, p38 binds to auto-poly ADP-ribosylated (PARylated) PARP1 resulting in the covalent PARylation of p38 by PARP1, thereby promoting the retention and activity of p38 in the nucleus. In addition, PARylation of HuR facilitates the phosphorylation of HuR at the serine 197 site mediated by p38, which then increases the translocation of HuR to the cytoplasm, ultimately stabilizing the inflammation-associated mRNA expression at the post-transcriptional level.

Human antigen R: Exploring its inflammatory response impact and significance in cardiometabolic disorders.

RNA-binding proteins (RBPs) play a crucial role in the regulation of posttranscriptional RNA networks, which can undergo dysregulation in many pathological conditions. Human antigen R (HuR) is a highly researched RBP that plays a crucial role as a posttranscriptional regulator. HuR plays a crucial role in the amplification of inflammatory signals by stabilizing the messenger RNA of diverse inflammatory mediators and key molecular players. The noteworthy correlations between HuR and its target molecules, coupled with the remarkable impacts reported on the pathogenesis and advancement of multiple diseases, position HuR as a promising candidate for therapeutic intervention in diverse inflammatory conditions. This review article examines the significance of HuR as a member of the RBP family, its regulatory mechanisms, and its implications in the pathophysiology of inflammation and cardiometabolic illnesses. Our objective is to illuminate potential directions for future research and drug development by conducting a comprehensive analysis of the existing body of research on HuR.

UBE4B regulates p27 expression in A549 NSCLC cells through regulating the interaction of HuR and the p27 5' UTR.

Ubiquitination factor E4B (UBE4B) has a tumor-promoting effect, demonstrated by its aberrant expression in various types of cancers, and in vitro studies have shown that the retardation of cancer cell proliferation can be induced by targeting UBE4B. However, the molecular pathways through which UBE4B exerts its oncogenic activities have not yet been clearly identified and existing knowledge is limited to p53 and its subsequent downstream targets. In this study, we demonstrated that UBE4B regulates p27 expression in A549 cells via the cap-independent translation pathway following treatment with rapamycin and cycloheximide (CHX). Subsequently, we identified that UBE4B regulates p27 translation by regulating the interaction between human antigen R (HuR) and the p27 internal ribosomal entry site (IRES). First, UBE4B interacts with HuR, which inhibits p27 translation through the IRES. Secondly, the interaction between HuR and the p27 IRES was diminished by UBE4B depletion and enhanced by UBE4B overexpression. Finally, HuR depletion-induced growth retardation, accompanied by p27 accumulation, was restored by UBE4B overexpression. Collectively, these results suggest that the oncogenic properties of UBE4B in A549 cells are mediated by HuR, suggesting the potential of targeting the UBE4B-HuR-p27 axis as a therapeutic strategy for lung cancer.

HuR facilitates miR-93-5p-induced activation of MAP3K2 translation via MAP3K2 3'UTR ARE2 in hepatocellular carcinoma.

MicroRNAs (miRNAs) can positively regulate gene expression through an unconventional RNA activation mechanism involving direct targeting 3' untranslated regions (UTRs). Our prior study found miR-93-5p activates mitogen-activated protein kinase kinase kinase 2 (MAP3K2) in hepatocellular carcinoma (HCC) via its 3'UTR. However, the underlying mechanism remains elusive. Here, we identified two candidate AU-rich element (ARE) motifs (ARE1 and ARE2) adjacent to the miR-93-5p binding site located within the MAP3K2 3'UTR using AREsite2. Luciferase reporter and translation assays validated that only ARE2 participated in MAP3K2 activation. Integrative analysis revealed that human antigen R (HuR), an ARE2-associated RNA-binding protein (RBP), physically and functionally interacted with the MAP3K2 3'UTR. Consequently, an HuR-ARE2 complex was shown to facilitate miR-93-5p-mediated upregulation of MAP3K2 expression. Furthermore, bioinformatics analysis and studies of HCC cells and specimens highlighted an oncogenic role for HuR and positive HuR-MAP3K2 expression correlation. HuR is also an enhancing factor in the positive feedback circuit comprising miR-93-5p, MAP3K2, and c-Jun demonstrated in our prior study. The newly identified HuR-ARE2 involvement enriches the mechanism of miR-93-5p-driven MAP3K2 activation and suggests new therapeutic strategies warranted for exploration in HCC.

A Novel Mechanism Linking Melatonin, Ferroptosis and Microglia Polarization via the Circodz3/HuR Axis in Subarachnoid Hemorrhage.

A subarachnoid hemorrhage (SAH) is life-threatening bleeding into the subarachnoid space that causes brain damage. Growing evidence has suggested that melatonin provides neuroprotection following SAH. Exploring the mechanisms underlying melatonin-mediated neuroprotection contributes to its clinical application in SAH. The plasma and cerebrospinal fluid (CSF) were collected from SAH patients, and SAH mice were established via pre-chiasmatic injection. Circodz3 expression, levels of IL-1ß and TNF-α, brain water content, neurological and beam-waling scores were determined. Ferroptosis was evaluated by analyzing levels of iron, lipid ROS, MDA, and GSH. The colocalization of circodz3 and Iba-1 was analyzed by immunofluorescence staining. Interaction of circodz3 and HuR was determined with RNA pull-down and RNA immunoprecipitation assays. Herein, we found that circodz3 was highly abundant in SAH patients and mice. Colocalization of circodz3 and Iba-1 in the left hemisphere of SAH mice suggested the implication of circodz3 in regulating microglia activation following SAH. Melatonin alleviated brain edema, neurological impairment, and microglia activation and inhibited circodz3 expression in SAH mice. Moreover, melatonin inhibited M1 polarization, oxidative stress and ferroptosis and restrained circodz3 expression in primary microglia following SAH. These effects were abrogated by circodz3 overexpression. Circodz3 knockdown inhibited ferroptosis and M1 polarization of BV2 microglia after SAH. Circodz3 interacted with HuR to facilitate ß-Trcp1-mediated ubiquitination and degradation, thus restraining the expression of SLC7A11 and GPX4. Collectively, melatonin exerted neuroprotection following SAH via inhibiting ferroptosis and M1 polarization through the circodz3/HuR axis. Our study suggests potential application of melatonin in the treatment of SAH.

RUNX1, FUS, and ELAVL1-induced circPTPN22 promote gastric cancer cell proliferation, migration, and invasion through miR-6788-5p/PAK1 axis-mediated autophagy.

BACKGROUND: An increasing number of studies have demonstrated the association of circular RNAs (circRNAs) with the pathological processes of various diseases and their involvement in the onset and progression of multiple cancers. Nevertheless, the functional roles and underlying mechanisms of circRNAs in the autophagy regulation of gastric cancer (GC) have not been fully elucidated. METHODS: We used transmission electron microscopy and the mRFP-GFP-LC3 dual fluorescent autophagy indicator to investigate autophagy regulation. The cell counting kit-8 assay, colony formation assay, 5-ethynyl-2'-deoxyuridine incorporation assay, Transwell assay, and Western blot assay were conducted to confirm circPTPN22's influence on GC progression. Dual luciferase reporter assays validated the binding between circPTPN22 and miR-6788-5p, as well as miR-6788-5p and p21-activated kinase-1 (PAK1). Functional rescue experiments assessed whether circPTPN22 modulates PAK1 expression by competitively binding miR-6788-5p, affecting autophagy and other biological processes in GC cells. We investigated the impact of circPTPN22 on in vivo GC tumors using a nude mouse xenograft model. Bioinformatics tools predicted upstream regulatory transcription factors and binding proteins of circPTPN22, while chromatin immunoprecipitation and ribonucleoprotein immunoprecipitation assays confirmed the binding status. RESULTS: Upregulation of circPTPN22 in GC has been shown to inhibit autophagy and promote cell proliferation, migration, and invasion. Mechanistically, circPTPN22 directly binds to miR-6788-5p, subsequently regulating the expression of PAK1, which activates protein kinase B (Akt) and extracellular signal-regulated kinase (Erk) phosphorylation. This modulation ultimately affects autophagy levels in GC cells. Additionally, runt-related transcription factor 1 (RUNX1) negatively regulates circPTPN22 expression, while RNA-binding proteins such as FUS (fused in sarcoma) and ELAVL1 (recombinant ELAV-like protein 1) positively regulate its expression. Inhibition of the autophagy pathway can increase FUS expression, further upregulating circPTPN22 in GC cells, thereby exacerbating the progression of GC. CONCLUSION: Under the regulation of the transcription factor RUNX1 and RNA-binding proteins FUS and ELAVL1, circPTPN22 activates the phosphorylation of Akt and Erk through the miR-6788-5p/PAK1 axis, thereby modulating autophagy in GC cells. Inhibition of autophagy increases FUS, which in turn upregulates circPTPN22, forming a positive feedback loop that ultimately accelerates the progression of GC.

DNMT3a-mediated upregulation of the stress inducible protein sestrin-2 contributes to malignant transformation of human bronchial epithelial cells following nickel exposure.

BACKGROUND: Nickel is a confirmed human lung carcinogen. Nonetheless, the molecular mechanisms driving its carcinogenic impact on lung tissue remain poorly defined. In this study, we assessed SESN2 expression and the signaling pathways responsible for cellular transformation in human bronchial epithelial cells (HBECs) as a result of nickel exposure. METHODS: We employed the Western blotting to determine the induction of SESN2 by nickel. To clarify the signaling pathways leading to cellular transformation following nickel exposure, we applied techniques such as gene knockdown, methylation-specific PCR, and chromatin immunoprecipitation. RESULT: Exposure to nickel results in the upregulation of SESN2 and the initiation of autophagy in human bronchial epithelial cells (HBECs). This leads to degradation of HUR protein and consequently downregulation of USP28 mRNA, PP2AC protein, ß-catenin protein, and diminished VHL transcription, culminating in the accumulation of hypoxia-inducible factor-1α (HIF-1α) and the malignant transformation of these cells. Mechanistic studies revealed that the increased expression of SESN2 is attributed to the demethylation of the SESN2 promoter induced by nickel, a process facilitated by decreased DNA methyl-transferase 3 A (DNMT3a) expression, while The downregulation of VHL transcription is linked to the suppression of the PP2A-C/GSK3ß/ß-Catenin/C-Myc pathway. Additionally, we discovered that SESN2-mediated autophagy triggers the degradation of HUR protein, which subsequently reduces the stability of USP28 mRNA and inhibits the PP2A-C/GSK3ß/ß-Catenin pathway and c-Myc transcription in HBECs post nickel exposure. CONCLUSION: Our results reveal that nickel exposure leads to the downregulation of DNMT3a, resulting in the hypomethylation of the SESN2 promoter and its protein induction. This triggers autophagy-dependent suppression of the HUR/USP28/PP2A/ß-Catenin/c-Myc pathway, subsequently leading to reduced VHL transcription, accumulation of HIF-1α protein, and the malignant transformation of human bronchial epithelial cells (HBECs). Our research offers novel insights into the molecular mechanisms that underlie the lung carcinogenic effects of nickel exposure. Specifically, nickel induces aberrant DNA methylation in the SESN2 promoter region through the decrease of DNMT3a levels, which ultimately leads to HIF-1α protein accumulation and the malignant transformation of HBECs. Specifically, nickel initiates DNA-methylation of the SESN2 promoter region by decreasing DNMT3a, ultimately resulting in HIF-1α protein accumulation and malignant transformation of HBECs. This study highlights DNMT3a as a potential prognostic biomarker or therapeutic target to improve clinical outcomes in lung cancer patients.

Expressions of HuR, Methyl-HuR and Phospho-HuR in Endometrial Endometrioid Adenocarcinoma Are Associated with Clinical Features.

HuR regulates cytoplasmic mRNA stability and translatability, with its expression correlating with adverse outcomes in various cancers. This study aimed to assess the prognostic value and pro-oncogenic properties of HuR and its post-translational isoforms methyl-HuR and phospho-HuR in endometrial adenocarcinoma. Examining 89 endometrioid adenocarcinomas, we analyzed the relationship between HuR nuclear or cytoplasmic immunostaining, tumor-cell proliferation, and patient survival. HuR cytoplasmic expression was significantly increased in grade 3 vs. grade 1 adenocarcinomas (p < 0.001), correlating with worse overall survival (OS) (p = 0.02). Methyl-HuR cytoplasmic expression significantly decreased in grade 3 vs. grade 1 adenocarcinomas (p < 0.001) and correlated with better OS (p = 0.002). Phospho-HuR nuclear expression significantly decreased in grade 3 vs. grade 1 adenocarcinomas (p < 0.001) and non-significantly correlated with increased OS (p = 0.06). Cytoplasmic HuR expression strongly correlated with proliferation markers MCM6 (rho = 0.59 and p < 0.001) and Ki67 (rho = 0.49 and p < 0.001). Conversely, these latter inversely correlated with cytoplasmic methyl-HuR and nuclear phospho-HuR. Cytoplasmic HuR expression is a poor prognosis marker in endometrioid endometrial adenocarcinoma, while cytoplasmic methyl-HuR and nuclear phosphoHuR expressions are markers of better prognosis. This study highlights HuR as a promising potential therapeutic target, especially in treatment-resistant tumors, though further research is needed to understand the mechanisms regulating HuR subcellular localization and post-translational modifications.

SUMOylation controls Hu antigen R posttranscriptional activity in liver cancer.

The posttranslational modification of proteins critically influences many biological processes and is a key mechanism that regulates the function of the RNA-binding protein Hu antigen R (HuR), a hub in liver cancer. Here, we show that HuR is SUMOylated in the tumor sections of patients with hepatocellular carcinoma in contrast to the surrounding tissue, as well as in human cell line and mouse models of the disease. SUMOylation of HuR promotes major cancer hallmarks, namely proliferation and invasion, whereas the absence of HuR SUMOylation results in a senescent phenotype with dysfunctional mitochondria and endoplasmic reticulum. Mechanistically, SUMOylation induces a structural rearrangement of the RNA recognition motifs that modulates HuR binding affinity to its target RNAs, further modifying the transcriptomic profile toward hepatic tumor progression. Overall, SUMOylation constitutes a mechanism of HuR regulation that could be potentially exploited as a therapeutic strategy for liver cancer.

HuR-positive stress granules: Potential targets for age-related osteoporosis.

Aging impairs osteoblast function and bone turnover, resulting in age-related bone degeneration. Stress granules (SGs) are membrane-less organelles that assemble in response to stress via the recruitment of RNA-binding proteins (RBPs), and have emerged as a novel mechanism in age-related diseases. Here, we identified HuR as a bone-related RBP that aggregated into SGs and facilitated osteogenesis during aging. HuR-positive SG formation increased during osteoblast differentiation, and HuR overexpression mitigated the reduction in SG formation observed in senescent osteoblasts. Moreover, HuR positively regulated the mRNA stability and expression of its target ß-catenin by binding and recruiting ß-catenin into SGs. As a potential therapeutic target, HuR activator apigenin (API) enhanced its expression and thus aided osteoblasts differentiation. API treatment increased HuR nuclear export, enhanced the recruitment of ß-catenin into HuR-positive SGs, facilitated ß-catenin nuclear translocation, and contributed osteogenesis. Our findings highlight the roles of HuR and its SGs in promoting osteogenesis during skeletal aging and lay the groundwork for novel therapeutic strategies against age-related skeletal disorders.

LncRNA HOST2 promotes NSUN2-mediated breast cancer progression via interaction with ELAVL1.

Breast cancer (BC) is the most prevalent malignant tumor in women worldwide with high morbidity and mortality. NSUN2, a crucial RNA methyltransferase, plays a pivotal role in regulating the proliferation and metastasis of tumor cells. Our study demonstrated that NSUN2 is upregulated in BC tissues and cell lines, and its high expression is associated with a poor prognosis in BC patients. Knockout of NSUN2 exerted inhibitory effects on the proliferation and migration of BC cells in vitro and in vivo. Mechanistic investigations revealed that the RNA-binding protein ELAVL1 can bind to NSUN2 mRNA and increase its stability. Additionally, we identified HOST2, a long non-coding RNA, as a key player in blocking the ubiquitin-dependent proteasomal degradation of ELAVL1, thereby influencing the stability of NSUN2 mRNA. In conclusion, this study revealed for the first time that HOST2 maintains NSUN2 mRNA stability by blocking ubiquitin-dependent degradation of ELAVL1, which in turn affects BC progression. HOST2/ELAVL1/NSUN2 oncogenic cascade has the potential to be a novel therapeutic target for BC.

The LEPIS-HuR-TMOD4 axis regulates hepatic cholesterol homeostasis and accelerates atherosclerosis.

BACKGROUND AND AIMS: Long noncoding RNAs (lncRNAs) play important roles in the progression of atherosclerosis. In this study, we identified an uncharacterized lncRNA, Liver Expressions by PSRC1 Induced Specifically (LEPIS). This study aimed to clarify the mechanism though which LEPIS affects atherosclerosis (AS). METHODS: The expression of LEPIS and its potential target, tropomodulin 4 (TMOD4), was increased in the livers of ApoE-/- mice fed a high-fat diet (HFD). An ApoE-/- mouse model in which LEPIS or TMOD4 was overexpressed in the liver was established. The plaque load in the aorta was assessed, plasma was collected to measure blood lipid levels, and the liver was collected to study cholesterol metabolism. RESULTS: We found that both LEPIS and TMOD4 increased the AS burden and reduced hepatic cholesterol levels. A further study revealed that LEPIS and TMOD4 affected the expression of genes related to hepatic cholesterol homeostasis, including proprotein convertase subtilisin/kexin type 9 (PCSK9) and low-density lipoprotein receptor (LDLR), which are closely related to hypercholesterolemia. Mechanistically, human antigen R (HuR), an RNA-binding protein (RBP), was shown to be critical for the regulation of TMOD4 by LEPIS. Furthermore, we found that verexpression of LEPIS promoted the shuttling of HuR from the nucleus to the cytoplasm, enhanced the stability of TMOD4 mRNA, and in turn promoted the expression of TMOD4. In addition, TMOD4 was found to affect intracellular cholesterol levels through PCSK9. CONCLUSIONS: These results suggest that the LEPIS-HuR-TMOD4 axis is a potential intervention target for dysregulated hepatic cholesterol homeostasis and AS and may provide the basis for further reductions in the circulating LDL-C concentration and arterial plaque burden.

ZBTB7A regulates LncRNA HOTAIR-mediated ELAVL1/SOX17 axis to inhibit malignancy and angiogenesis in endometrial carcinoma.

BACKGROUND: Endometrial cancer (EC) is the sixth most frequent cancer in women worldwide and has higher fatality rates. The pathophysiology of EC is complex, and there are currently no reliable methods for diagnosing and treating the condition. Long non-coding RNA (lncRNA), according to mounting evidence, is vital to the pathophysiology of EC. HOTAIR is regarded as a significant prognostic indicator of EC. ZBTB7A decreased EC proliferation and migration, according to recent studies, however the underlying mechanism still needs to be clarified. METHODS: The research utilized RT-qPCR to measure HOTAIR expression in clinical EC tissues and various EC cell lines. Kaplan-Meier survival analysis was employed to correlate HOTAIR levels with patient prognosis. Additionally, the study examined the interaction between ZBTB7A and HOTAIR using bioinformatics tools and ChIP assays. The experimental approach also involved manipulating the expression levels of HOTAIR and ZBTB7A in EC cell lines and assessing the impact on various cellular processes and gene expression. RESULTS: The study found significantly higher levels of HOTAIR in EC tissues compared to adjacent normal tissues, with high HOTAIR expression correlating with poorer survival rates and advanced cancer characteristics. EC cell lines like HEC-1 A and KLE showed higher HOTAIR levels compared to normal cells. Knockdown of HOTAIR in these cell lines reduced proliferation, angiogenesis, and migration. ZBTB7A was found to be inversely correlated with HOTAIR, and its overexpression led to a decrease in HOTAIR levels and a reduction in malignant cell behaviors. The study also uncovered that HOTAIR interacts with ELAVL1 to regulate SOX17, which in turn activates the Wnt/ß-catenin pathway, promoting malignant behaviors in EC cells. CONCLUSION: HOTAIR is a critical regulator in EC, contributing to tumor growth and poor prognosis. Its interaction with ZBTB7A and regulation of SOX17 via the Wnt/ß-catenin pathway underlines its potential as a therapeutic target.